Fructose has been associated with negative adverse health effects. A new study published in the PLOS One journal has revealed that excessive consumption may be a risk factor affecting a variety of diseases. Fructose is generally a carbohydrate that occurs naturally in fruits and vegetable and is used as an added sugar in sugary drinks and processed foods.

The researchers have investigated how these two types of sugar affect interactions between the gastrointestinal tract and the brain by using combined pharmacological and imaging methods such as functional magnetic resonance imaging (MRI).

“The study may provide the first key findings about the lack of satiety and rewarding effects triggered by fructose,” said lead authors Dr Bettina Wölnerhanssen and Dr Anne Christin Meyer-Gerspach.

The research findings indicate that unlike glucose, fructose is less effective at creating feelings of satiety and stimulating the reward system in the brain. Magnetic Resonance Imaging of the brain revealed that the two types of sugar differed greatly in terms of network activation within the hippocampus and amygdala areas of the limbic system, i.e. the regions of the brain that regulate emotions and impulses.

The levels of satiety hormones in the blood barely or only minimally increased following fructose consumption. The subjective feeling of satiety also tended to be less affected by the consumption of fructose, leading to a excess consumption of food.

A previous study by the University of Utah has published a new study specifying that the fructose-glucose mixture found in high fructose corn syrup is more toxic than sucrose or table sugar. Currently it is estimated that 13 percent to 25 percent of Americans eat a diet that includes 25 percent or more of calories in the form of added sugars; the percentage of added sugars consumed by mice in the new study. “Added sugars” are sugars added during food processing or preparation and not already naturally in food, like in a piece of fruit. Generally 44& of the added sugar is sucrose and 42% is high fructose corn syrup.

The study used a mouse model to examine the adverse impact of high fructose corn syrup. “This is the most robust study showing there is a difference between high-fructose corn syrup and table sugar at human-relevant doses,” said biology professor Wayne Potts, senior author of the study.

The researchers use a new sensitive toxicity test and it was determined that female mice on the fructose glucose diet had death rates 1.87 times higher than females on the sucrose diet. They also produced 26.4 percent fewer offspring.

Concern has arisen over high fructose syrup as a few studies have documented increased diabetes-obesity-metabolic syndrome to increased exposure of the syrup in the 1970s, when sucrose was replaced by high corn fructose in the majority of food products.

Another study has confirmed the metabolic damage caused by fructose. Diabetes is estimated to impact on approximately 29 million people in the US, with another 86 million suffering from pre-diabetes. Added sugars such as fructose have been directly linked to diabetes and pre-diabetes.

“At current levels, added-sugar consumption, and added-fructose consumption in particular, are fueling a worsening epidemic of type 2 diabetes,” said lead author James J. DiNicolantonio, PharmD, a cardiovascular research scientist at Saint Luke’s Mid America Heart Institute, Kansas City, MO. “Approximately 40% of U.S. adults already have some degree of insulin resistance with projections that nearly the same percentage will eventually develop frank diabetes.”

Excess fructose consumption impacts negatively on overall metabolism and global insulin resistance. Other dietary sugars don’t appear to have the same negative effects. Indeed several clinical trials have shown that compared to glucose or starch, isocaloric exchange with fructose or sucrose leads to increases in fasting insulin, fasting glucose, and the insulin/glucose responses to a sucrose load. “This suggests that sucrose (in particular the fructose component) is more harmful compared to other carbohydrates,” said Dr. DiNicolantonio.

Recent studies indicate that replacing glucose-only starch with fructose-containing table sugar (sucrose) result in significant adverse metabolic effects. The adverse effects are dose dependent and increase with with greater proportions of added fructose in the diet.

The researchers recommend limiting fructose to world health guidelines which specify that added sugars should make up no more than 10% of an entire day’s caloric intake, with a proposal to lower this level to 5% or less for optimal health. Although fructose is found naturally in fructose there are no negative effects associated with the natural version. Instead consuming fruits and vegetables protects against diabetes and broader cardiometabolic dysfunction.